Echinoderms

Name Means:

Echino- Spiny

Derm- Skin

About 7,000 species

No Head! No Brain!

No ventral, dorsal, posterior, or anterior sides!

Do have oral (mouth) and aboral sides.

Characteristics

Symmetry:

Larvae are Bilateral

Adults are radial (body rounded) with the following forms:

Rounded Body

Cylindrical

Star-shaped

Larvae of a Sea

Urchin

http://en.wikipedia.org/wiki/Image:Pluteus001.jpghttp://en.wikipedia.org/wiki/Image:Pluteus001.jpg

Characteristics

Body Covering:

Endoskeleton of calcareous plates (ossicles)

Covered with spines

Covered by epidermis

http://en.wikipedia.org/wiki/Image:Red-knobbed.starfish.arp.jpghttp://en.wikipedia.org/wiki/Image:Red-knobbed.starfish.arp.jpg

Characteristics Water Vascular System:

Hydraulic system with canals and specialized feet.

Tube feet are for: Locomotion and attachment (slow bottom crawlers)

Food getting

When filled with water

extended

http://en.wikipedia.org/wiki/Image:Starfish.jpghttp://en.wikipedia.org/wiki/Image:Starfish.jpg

Characteristics

Tube feet or Podia

Muscular tubes that project through pores in body wall

Outer end usually has a sucker, but not in all species

Located in the ambulacral groove on oral side of each ray

Characteristics

Body Cavity:

Large fluid filled body cavity (coelom)

Fluid contains amoebocytes

Distribution of digested food, gases, and wastes

Characteristics

Digestive System: Mouth- oral side, center

Stomach- Located in central disk

2 chambers Cardiac

Lower

Largest

Everted during feeding

Pyloric

Upper

Connected to pyloric ceca in each ray by small ducts

Characteristics Digestive System:

Pyloric ceca

Digestive glands

Esophagus

Short tube connecting mouth the stomach

Food

Most are carnivores eating mollusks, crustaceans, and tube worms

Characteristics Feeding

Eversion of stomach

Very little feces because very little indigestible material is ingested

Characteristics

Excretory Systems

No specialized system

Amoebocytes gather waste

Waste given off through dermal branchiae

Characteristics

Respiratory System:

Dermal branchiae (skin gills)

Project through pores in body wall

Gas exchange takes place here

http://en.wikipedia.org/wiki/Image:Henricia-sanguinolenta.jpghttp://en.wikipedia.org/wiki/Image:Henricia-sanguinolenta.jpg

Characteristics Nervous System:

Very simple, no brain

Nerve ring

Eyespot (ocelli) at tip of each ray

Sea stars usually more active at night- they are photonegative

http://en.wikipedia.org/wiki/Image:Ochre_sea_star_on_beach%2C_Olympic_National_Park_USA.jpghttp://en.wikipedia.org/wiki/Image:Ochre_sea_star_on_beach%2C_Olympic_National_Park_USA.jpg

Characteristics

Circulatory System

Poorly developed

Series of ill-defined channels

Ring vessel around mouth

Radial vessels in each ray

Characteristics Reproductive System

Dioecious

Glands in each ray

Eggs and sperm shed into water in early summer

Fertilization is external

Larvae stages are free swimming!

Regeneration (Asexual) Can regenerate lost arms

Classification Class Asteroidea (Sea Stars- true

starfish)

Luida alternata

Astropecten

Asterias

http://en.wikipedia.org/wiki/Image:Astropecten_irregularis.jpghttp://en.wikipedia.org/wiki/Image:Astropecten_irregularis.jpghttp://en.wikipedia.org/wiki/Image:Asterias_rubens.jpghttp://en.wikipedia.org/wiki/Image:Asterias_rubens.jpg

Classification

Description

Star shaped; most with 5 arms

Arms not sharply marked off from disc

Ambulacral grooves with up to 50 tube feet on oral side

Tube feet with suckers

Classification

Description

Anus and madreporite (pore through which water enters the water vascular system) on aboral surface

Gonads located in rays

Digestive glands located in rays

Classification

Class Echinoidea

Examples:

Sea urchins- Arabacia

Sea biscuits

Sand dollars- Mellita

Classification Description

Globular in shape

No arms

Compact skeleton or test of calcium carbonate

Movable spines for locomotion

Ambulacral groove covered with ossicles

5 rows of Tube feet with suckers

Urchins eat plants, algae, and sometimes small animals

Mouth on bottom

Anus on top

http://en.wikipedia.org/wiki/Image:Sea_urchin_tests.jpghttp://en.wikipedia.org/wiki/Image:Sea_urchin_tests.jpg

Aristotles Lantern

Classification Class Ophioroidea

Examples:

Brittle stars

Basket stars

Classification Description

Star shaped

Arms sharply marked off from disc

Ambulacral grooves absent or covered by ossicles

Tube feet without suckers and not used for locomotion

Feed on particulate matter or small animals they pick up from bottom

No anus

Classification

Class Holothuroidea

Examples:

Sea Cucumbers

Classification Description

Cucumber shaped

Endoskeleton made up of microscopic calcareous spicules scattered through warty skin

No Arms

Spines absent

Tube feet with suckers

Circumoral tentacles

Classification Description

Some burrow to hide

Some secrete a toxic substance

self mutilation when irritated

Will discharge gut and other internal organs through mouth

(evisceration)

Classification

Class Crinoidea

Examples:

Feather stars

Crawl

Shallow and deep

Sea Lilies

Attached to bottom

Classification

Description

Suspension feeder

Feathery arms